<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
    <input type="text">
    <textarea></textarea>
</body>
</html>
<script>
    var ipt=document.querySelector('input')
    var tet=document.querySelector('textarea')
    ipt.onfocus=function(){
        ipt.value=''
    }
    ipt.onblur=function(){
        ipt.value='鸡你太美'
    }
    tet.onblur=function(){
        tet.value='厉不厉害你坤哥'
    }
</script>